Helping to accurately measure sea surface height: the NASA instrument suite on OSTM (Ocean Surface Topography Mission)

OSTM (Ocean Surface Topography Mission) will provide continuity of ocean topography measurements that began with TOPEX/Poseidon and are currently being carried out by Jason. Measurements made by the three missions will allow scientists to better understand ocean circulation, climate change processes, and sea level rise on a multi-decadal scale. While CNES (Centre National d'Etudes Spatiales) will provide the primary satellite instrument, a nadir-pointed altimeter, and a precision orbit determination system, NASA (National Aeronautics and Space Administration) will provide an instrument suite to provide the necessary measurement accuracy. The AMR (Advanced Microwave Radiometer) will measure atmospheric water vapor content to determine how it affects the accuracy of the altimeter readings. The GPSP (Global Positioning System Payload) will be used to accurately pinpoint the position of the satellite above the ocean surface. Finally, there is the LRA (Laser Retroreflector Array), a passive, supporting instrument that will allow ground-based laser ranging stations to also pinpoint the position of the satellite. Both the GPSP and LRA will be used to enhance the precision orbit determination system performance. The instruments are now undergoing ground test. In conjunction with in-flight calibration and validation activities these efforts will help to ensure mission success.